Stereophonograph cartridge



Dec. 2, 1969 J. F. (ERA DO STEREOPHONOGRAPH CARTRIDGE 3 Sheets-Sheet 1 Filed Sept. 13, 1966 Dec. 2, 1969 J. F. GRADO 3,482,061

STEREOPHQNOGRAPH CARTRIDGE Filed Sept. 15, 1966 s Sheets-Sheet 2 W 2mm United States Patent Oflice 3,482,061 Patented Dec. 2, 1969 3,482,061 STEREOPHONOGRAPH CARTRIDGE Joseph F. Grado, 4614 7th Ave., Brooklyn, N.Y. 11220 Filed Sept. 13, 1966, Ser. No. 579,133 Int. Cl. H04r 1/16, 11/08 U.S. Cl. 179100.41 11 Claims ABSTRACT OF THE DISCLOSURE A stereo cartridge having a block assembly with two channels and channel damping laminations is provided with signal generators in each channel. One end of each of the generators is extended past the channels to engage a yoke, while the opposite ends of the generators are secured in their respective channels by tightening a clamp cap overlying both the channels and generators. The damping lamination is also applied along the block assembly which abuts the yoke connected to the stylus assembly. The yoke can be positioned relative to each generator. The stylus assembly further includes a mounting plate which is adjustable relative to the block assembly to change the compliance of the stylus assembly.

This invention relates to phonograph cartridges, and more particularly to a construction therefor which permits uniformity in massaproduced units together with mechanisms for each unit to enable adjustments with respect to the surrounding environment and within the cartridge itself for state-of-the-art performance.

Stereo cartridges are characterized by two generators placed approximately at a right angle to each other. The generators themselves may be of many types, e.g., crystal, ceramic, capacitive, etc. In one type of stereo cartridge, a stylus beam is mounted with its longitudinal axis approximately coincidental with the point of intersection of two lines, each drawn through a respective generator and at an approximate angle of 45 degrees from the vertical plane of symmetry. One end of the beam is secured to a mount and the other contains a stylus which tracks a record groove. As the stylus and beam move, multiple components of motion are applied to the respective generators. The generators, in turn, provide the electrical signals which are fed to the amplifying units.

The compliance of a cartridge system is determined primarily by the ratio of the stylus beam length between the stylus itself and the point of effective contact with the generators, and the length of the beam continuation from this point of effective contact to the pivot point of the beam. In prior art cartridges the compliance of each unit is fixed-even though for optimum performance the compliance should be matched to the mass of the tone arm in which the cartridge is used.

One object of my invention is the provision of a cartridge in which the compliance may be adjusted by the user to optimally match the cartridge compliance with the one arm mass.

The performance of a prior art cartridge is generally dependent upon uniformity of material structure and dimensional tolerance. Less than optimum performance usually results.

Another object of my invention is the provision of a cartridge in which adjustments may be made for optimum electrical and mechanical performance independent of tone arm mass, even after final assembly and despite variations in material structure and dimensional tolerance.

Another object of my invention is the provision of such an adjustable cartridge in which the adjustment of each generator is independent of the other to permit accurate matching of the generators for symmetrical voltage output.

Prior art cartridges often utilize grease or other viscous material for damping non-linear mechanical effects. But the prior art damping techniques are not only less than fully effective, they also give rise to non-uniformity, both in individual units and in production quantities.

Another object of my invention is to insure consistent application of damping material for maximum uniformity in production.

Prior art cartridges generally exhibit poor mechanical precision in the mechanical suspension which transmits motion from the stylus to the individual generators. For maximum performance the motion of the stylus should be transmitted to the generators, through the mechanical coupling of the stylus beam and its mounting, as faithfully as possible.

Another object of my invention is the provision of a rugged stylus beam of sufiiciently low mass such that it is resonant beyond the audible range.

Another object of my invention is the provision of a low-cost mechanical suspension of such high precision that the resonant free tracing motion of the stylus in a record groove is transmitted to the generators for maximally low-distortion playback.

Another object of my invention is the provision of a rigid, light mass, internally damped stylus beam which has a single, accurate pivot point at all frequencies and which is simple in construction for low-cost manufacturing and production uniformity.

Another object of my invention is the provision of a simple replaceable stylus assembly which permits automatic positioning of the stylus beam in the cartridge for optimum mechanical and electrical performance.

Another object of my invention is the provision of a rigid mounting for the generators such that free generator beam fiexure is the only source of electrical output.

Still another object of my invention is the provision of a generator mounting which is simple in construction for low-cost manufacturing and production uniformity.

The cartridge of the illustrative embodiment of my invention is characterized by rigidity and light weight, yet with virtually distortionless response; by uniformity of low-cost mechanical precision, yet with variable compli ance and adjustable performance characteristics. The cartridge is comprised of four sub-assemblies: a housing, a generator block assembly, a stylus assembly and a cover with a spring lever. The generator block assembly, which includes a body, two generators, a generator clamp and a resilient yoke on the free ends of the generators, fits into the housing. The stylus assembly consists of the stylus beam in a mounting plate. The mounting plate is placed under the generator block with the stylus beam against the generator yoke. The spring lever of the cover secures the stylus mounting plate to the housing and generators block assembly.

The underside of the generator block body has a female V track and the stylus mounting plate has a V male counterpart. This permits relative longitudinal movement between the two to provide a variable compliance, yet provides a precision interlock for positioning the stylus plate to the generator block. A rigid structure is obtained because the spring lever on the cover locks the stylus assembly to the generator block. The lever spring forces the stylus mounting plate against the generator block at approximately the point where the stylus beam is secured to the mounting plate. The beam is thus freely movable within an overall absolutely rigid surrounding.

The generator block body has two grooves for holding the generators, which grooves are shaped to conform to the shape of the generators. At the front end, the free ends of the generators are embedded in an elastomeric yoke (e.g., made of resilient rubber), against which the stylus beam is placed. At the rear end the two generators are rigidly secured to the generator block by a conforming cap. The generators may also be rigidly mounted by adhesive or other alternatives. Damping material (e.g., grease) is placed between the yoke and the block and along the generator grooves between both faces of each generator and the groove walls. This damping material increases the resonant frequency of the generators while at the same time limiting their amplitude of motion, and damps resonant motion of the generator yoke structure. Unlike prior art designs, the regions in which the damping material is placed is rigidly defined to complement the generator shape. Accurate damping is achieved because the damping material covers the entire face of the generator with an even thickness so that all sections of the generator are optimally damped. Furthermore, because the thickness of the layers of damping material are fixed, every unit made can be to the same specifications.

It is to be understood that the various features of the illustrative embodiment of the invention may be used individually without each other; for maximum performance they should all be used together. These features include:

1) A stylus mounting plate movable in the longitudinal direction of the stylus beam with respect to the generator yoke position;

(2) A V-track alignment between the generator block and the stylus mounting plate;

(3) A lever spring arrangement for rigidly securing the stylus mounting plate to the generator block at the selected position for proper compliance;

(4) A swinging spring lever to facilitate independent replacement of the stylus assembly;

(5) Means for rigidly securing the rear ends of the generators to the generator block such that they are positioned in grooves shaped to conform to the shape of the generators with minimum clearance;

(6) Layers of damping material along the minimum clearance generator grooves in the generator block; and

(7) A rugged, low-mass, laminated stylus beam with an accurate pivot point.

Further objects, features and advantages of the invention will become apparent upon consideration of the following detailed description in conjunction with the drawing in which:

FIG. 1 is a top plan view of an illustrative embodiment of the invention in its assembled condition;

FIG. 2 is a side elevational view;

FIG. 3 is a front elevational view;

FIG. 4 is a bottom plan view;

FIG. 5 is an exploded upside-down view of the disassembled cartridge;

FIG. 6 is a top plan view of the stylus mounting plate;

FIG. 7 is an upside-down sectional view of the stylus mounting plate taken along line 77 of FIG. 6;

FIG. 8 is a sectional view of the stylus mounting plate taken along line 88 of FIG. 7;

FIG. 9 is a bottom view of the stylus beam;

FIG. 10 is a sectional view of the stylus beam taken along line 10-10 of FIG. 9;

FIG. ll is a bottom plan view of the generator block;

FIG. 12 is an upside-down side elevational view of the generator block;

FIG. 13 is an upside-down front elevational view of the generator block;

FIG. 14 is an upside-down rear elevational view of the generator block;

FIG. 15 is a bottom plan view of the generator block placed in the housing, with the stylus mounting plate and cover removed;

FIG. 16 is an upside-down sectional view taken along line 1616 of FIG. 15, together with the corresponding sectional view of the stylus mounting plate;

FIG. 17 is a sectional view of the assembled unit taken along line 1717 of FIG. 15, with the stylus mounting plate and cover added;

FIG. 18 shows the positions of the generator block and stylus mounting plate for a first value of compliance;

FIG. 19 shows the positions of the generator block and stylus mounting plate for a second value of compliance; and

FIG. 20 is a front view of just the generator block and stylus mounting plate to show the relative positions of the stylus, yoke and generators.

Referring to FIG. 5, the four subassernblies of the illustrative cartridge are shown. Housing 26 encloses generator block 41 and includes two screwholes 22 which are used to mount the cartridge to the tone arm. (The cartridge pieces are shown upside-down for greatest clarity in this figure and many of the others.) Four grooves 47 are provided for holding the generator block pins 23 and 24. Two notches 31 on either side of the housing serve to secure cover 25 to the housing.

As seen best in FIGS. 16 and 17 the interior of the housing includes two lugs 81 which support the rectangular notch 32 of the generator block 41 at both sides thereof. Thus when the generator block is inserted into the housing, its position with respect to the housing is fixed. The block is held securely in the housing because it is slightly wider than the dimension between walls 49 of the housing. Preferably, the block is also plastic welded to the housing.

As will be described below, generator block 41 has attached to it a generator sub-assembly which includes elastomeric yoke 43. Two gold leaf strips 40 are held against the two sides of each generator to electrically connect them to respective pins 23 or 24. The pins rest in grooves 47. Wires carried by the tone arm (not shown) connect the pins to the amplifying equipment.

Stylus mounting plate 27 (FIG. 6) has attached to it a flexible rod 56 (e.g., made of nylon or other plastic) which is encased by jacket 29 with stylus 28. It is this unit which is replaced when the stylus wears down or is damaged. The mounting plate rests in the V groove of the generator block and is capable of sliding movement along the generator block. Cover 25 is attached to the housing with sides 49 fitting into notches 31 (FIG. 5). The cover can be additionally secured to the housing with adhesive.

Lever spring 36 is shown in its open position in FIG. 5. If the spring is rotated degrees in the counter-clockwise direction the spring rests against mounting plate 27 to press it against the V groove of generator block 41. Frictional forces prevent the mounting plate from moving along the V grooves. Lugs 39 limit the spring movement in either direction on cover 25, as the spring is pivoted around pin 37. The assembled unit is best seen in FIG. 17. Mounting plate 27 can be forced back and forth in the direction of the arrow shown in FIG. 17 if sufficient force is applied to overcome the frictional force produced by spring 36. It is not necessary to move the spring to its open position if sufficient force is applied. As will be described below, the movement of mounting plate 27 controls the compliance of the stylus assembly.

FIGS. l4 show the assembled cartridge in various views.

FIGS. 9 and 10 show the stylus beam itself. The beam consists of a jacket 29 crimped at the forward end to hold a stylus 28. The cross-section of the jacket is shown in FIG. 10. The particular cross-section provides for great rigidity of the beam. Flexible rod 56 is inserted in the full length of the jacket. The jacket is then laminated by compression to the flexible rod. The free end of the flexible rod is attached to the stylus mounting plate 27 as shown in FIGS. 68.

The interior of the mounting plate is characterized by a double-V configuration as shown best in FIG. 7, numerals 57 designating the point of each V, The two V- meet at notch 58. The width of this notch is slightly less than the diameter of flexible rod 56. The free end of the flexible rod is pressed into this notch where it is tightly held. For the best possible attachment, solvent 59 (FIG. 8) is placed into notch 58 to bond the flexible rod to the mounting plate. As seen in FIG. 8, the rear end of jacket 29 is displaced from the forward end of notch 58 by a distance w. The distance w permits an accurate, free pivoting action of the beam about the front end of notch 58, while at the same maintaining the beam itself very rigid.

In the prior art, stylus beams have generally been constructed of lightweight material, such as aluminum, crimped at one end for attachment of a stylus, and secured at the other end to some sort of approximate pivoting mechanism. Since the beam must be precisely pivoted about this point of attachment, and the beam is of a rigid material, various difficulties have been encounered in providing precise pivotal movement. Furthermore, prior art beams have been characterized by natural resonances which give rise to distortion in the electrical output signals. These problems are overcome with the arrangement of FIGS. 6-10. The laminated beam provides the requisite rigidity and damping. The flexible rod along dimension w enables very precise pivotal movement.

The generator block sub-assembly is shown in FIGS. 11-16. The generator block 41 itself is provided with two parallel generator grooves in planes intersecting at an angle of 90 degrees, and having cross-sectional areas similar to but slightly larger than the shape of the cross-section of the generators. The width of each groove is just wide enough to allow a generator to fit therein with a minimum clearance. The generators 44 extend forward of the grooves where they are inserted into two slits in an elastomeric yoke 43.

At the rear end of block 41 the generator grooves terminate and the generators extend out past the grooves. A trapezoidal mounting plate 46 is placed above the rear ends of the generators and is attached to the generator block by screw 45 and bolt 72. A square washer 71 is provided so that the force of the screw is spread evenly over the top surface of trapezoidal cap 46. It is the cap which bears down against the rear ends of the generators (FIG. 14) to clamp the generators to the generator block and, at the same time, to secure the connections between the gold leaf strips 40 and the generators. Alternative means may be provided for the rigid mounting of the generators in the generator block 41.

The forward ends of the generator are embedded in the slits cut in yoke 43. The yoke can be moved slightly toward and away from the generator block. This is shown by dimensions x and y in FIGS. 11 and 12. These dimensions need not necessarily be equal, as will be described below. The bottom of yoke 43 is not flush against the generator block as shown by dimensions 14 and v in FIG. 13.

The generator sub-assembly is shown inserted in housing 26 in FIG. 15. When stylus mounting plate 27 is placed on top of generator block 41 (it is at the bottom thereof in actual use) it is seen that the two units have conforming V configurations which permit relative longitudinal movement but no transverse movement. With cover in place and lever spring 36 bearing against the stylus mounting plate, even longitudinal movement is prevented by the resulting friction in the absence of an externally applied force.

With the lever spring in the open position the stylus mounting plate may be removed for replacement. After the new stylus mounting plate is in place the lever spring is swung 90 degrees to its closed position to retain the plate in place.

The operation of the cartridge is as follows: It will be noted that the stylus beam rests against yoke 43 when the mounting plate is attached to the generator block. As the stylus tracks the record groove, the beam moves against the yoke. The components of motion in the directions of the generators, where their forward ends pass through the yoke, result in electrical signals which are picked up by the gold leaf wiring connections. These signals are then transmitted to the amplifying equipment.

The improved operating characteristics of my cartridge arise to a great extent from the manner of mounting the generators in the generator block. As in prior art designs, I also provide for damping with the use of grease or other viscous material. But the damping material is used diflerently. The damping material is placed between the bottom of the yoke and the generator block (dimensions a and v in FIG. 13), between the rear face of the yoke and the generator block (dimensions a and y in FIGS. 11 and 12) and along the generator channels in the generator block. The improved performance arises for a number of reasons.

Trapezoidal cap 46 rigidly secures the generator to the rear of the generator block. The front ends of the generators are free for movement. But between the front and rear ends of the generators, the generators are accurately restricted in movement. In the prior art the generators have been left free along their lengths or embedded in grease in a loose-fitting groove or channel. This resulted in non-uniformity in cartridges of each particular type. In my cartridge, the generators fit in the generator block channels with a minimum of clearance. Filling this clearance with damping material provides an effective lamination between the generators and the generator block. The minimum clearance provides a relatively tight fit but enables the generators to flex for proper operation in accordance with the motion of the stylus beam. Because the channels conform to the shape of the generators uniformity in mass-produced units is achieved. This uniformity is achieved without complex adjustment mechanisms simply by providing relatively tight-fitting channels (with thin layers of damping material on their walls). And the generators are secured to the block with a simple trapezoidal cap clamp 46.

The damping material provides the necessary damping by acting on the generators themselves within the channels. Contributions to the damping are provided both by the shear forces developed in the damping material along the rear face of the yoke (dimensions x and y) and by the compression forces developed in the damping mate rial between the yoke edges and the block (dimensions u and v). The damping both increases the resonant frequency of the combined unit and decreases the magnitudes of resonances.

The particular attachment of the generators to the yoke permits balancing of the channels. The relative magnitudes of the output signals of the two generators are determined in part by the shear action of the damping material in the respective dimensions x and y in FIGS. 11 and 12. Since the generators are secured to the yoke simply by being embedded in slits cut in the yoke, the relative x and y dimensions may be varied by pushing or pulling the yoke at one side thereof with respect to the respective generator. The manufacturer of the cartridge may test the relative strengths of the two output signals and adjust the yoke accordingly.

The compliance of the stylus assembly is determined by the ratio of dimension a to dimension b in FIGS. 18 and 19. Yoke 43 is fixed with respect to the generator block after its initial adjustment. But mounting plate 27 is free for longitudinal movement if sufi'icient external force is applied as described above. Movement of the mounting plate varies the point on the stylus beam which abuts against the yoke (FIGS. 18-20). This in turn varies the ratio of a and b. Rearward movement of mounting plate 27, shown in FIG. 19 by an increase of dimension a (w and a decrease of dimension b (11*), decreases the ratio b/a and thus decreases the compliance of the stylus assembly.

This variable compliance feature enables the cartridge to be used optimally with tone arms of different mass. Although the compliance can be varied it should be noted that the precision of the stylus beam operation is not sacrificed. The V conforming ridges of the generator block and the mounting plate prevent relative transverse movements for any position of the mounting plate. Spring 36 prevents any wobble between the two sub-assemblies.

Although the invention has been described with reference to a particular embodiment, it is to be understood that this embodiment is merely illustrative of the application of the principles and various features of the invention. Numerous modifications may be made therein and other arrangements may be devised without departing from the spirit and scope of the invention.

What is claimed is:

1. A phonograph cartridge comprising a generator block assembly having two parallel generator channels therein disposed in approximately perpendicular planes, two generators mounted in said channels, said channels having configurations for permitting said generators to fit therein with a minimum of clearance, means for rigidly securing said generators to said generator block assembly, and means for imparting motion to said generators, the plane of each of said channels being at an approximately 45 degree angle with respect to a vertical center plane passing through said generator block assembly and said generators extending past said channels at one end thereof, and said securing means including a cap having two oppositely disposed planar surfaces each at an approximately 45 degree angle with respect to a vertical center plane passing through the cap, said cap having a configuration such that when placed on said one end of said generators said planar surfaces abut against sides of said generators, and means for tightening said cap against said generators in said generator block assembly.

2. A phonograph cartridge in accordance with claim 1 wherein said motion imparting means is a yoke contacting said two generators, and further including a damping material lamination of said generator block assembly along said generator channels and along those surfaces abutting said yoke.

3. A phonograph cartridge in accordance with claim 2 further including a stylus assembly having a mounting plate selectively attachable to said generator block assembly with a stylus beam for contact with said yoke, and wherein said generator block assembly includes a locking member along the underside thereof, and said mounting plate includes a conforming locking member for preventing relative movement of said mounting plate with respect to said generator block assembly when said mounting plate is attached to said generator block assembly.

4. A phonograph cartridge in accordance with claim 3 further including a lever spring for bearing against the underside of said mounting plate to secure said mounting plate against said generator block assembly to provide sufiicient friction between said mounting plate and said generator block assembly to prevent movement of said mounting plate in the absence of an externally applied force.

5. A phonograph cartridge in accordance with claim 4 further including means for enabling movement of said lever spring to release said mounting plate.

6. A phonograph cartridge in accordance with claim 3 wherein said mounting plate is positionable to said generator block assembly such that the compliance of said stylus assembly may be adjusted to a tone arm in which the cartridge is used.

7. A phonograph cartridge in accordance with claim 2 further including means for positioning said yoke with respect to said generator block assembly for controlling the balance of said generators.

8. A phonograph cartridge in accordance with claim 3 wherein said stylus beam includes a flexible rod surrounded by a rigid jacket, said rod being secured to said mounting plate at the end thereof, and a stylus connected to the forward end of said jacket.

9. A phonograph cartridge comprising a generator block assembly having two parallel generator channels therein disposed in approximately perpendicular planes, two generators mounted in said channels, said channels having configurations for permitting said generators to fit therein with a minimum of clearance, means for rigidly securing said generators to said generator block assembly, and means for imparting motion to said generators, said motion imparting means being a yoke contacting said two generators, and further including a damping material lamination of said generator block assembly along said generator channels and along those surfaces abutting said yoke.

10. A phonograph cartridge comprising a generator block assembly, two generators, means for securing each of said generators to said generator block assembly, means for imparting motion to said generators, a mounting plate having a stylus assembly attached thereto, and means for selectively positioning said mounting plate with respect to said generator block assembly and said motion imparting means to adjust the compliance of said stylus assembly, said securing means including a cap having two inclined planar surfaces each conforming to a planar surface of a respective one of said generators, and means for tightening said cap to said generator block assembly to clamp ends of said generators thereto.

11. A phonograph cartridge comprising a generator block assembly, two generators, means for securing each of said generators to said generator block assembly, means for imparting motion to said generators, a mounting plate having a stylus assembly attached thereto, and means for selectively positioning said mounting plate with respect to said generator block assembly and said motion imparting means to adjust the compliance of said stylus assembly, said generator block assembly containing two generator channels conforming to said two generators with a minimum of clearance and wherein said phonograph cartridge further comprises a damping material lamination along said generator channels and a damping material lamination long all abutting surfaces of said motion imparting means and said generator block assembly.

References Cited UNITED STATES PATENTS 2,549,757 4/1951 Corbett 179-100.41 2,879,413 3/1959 Smith-Johannsen l79100.41 X 2,962,290 11/1960 Gunter et a1. 179--100.41 3,230,317 1/1966 Freise l79-100.41 3,233,047 2/1966 Weathers 179100.4l X 3,243,523 3/1966 Richter 179-10041 3,334,904 8/1967 Haines 179100.41 X

STANLEY M. URYNOWICZ, JR., Primary Examiner R. F. CARDILLO, JR., Assistant Examiner 

